Emissions tests are often part of the registration renewal ritual for many car owners. Some appreciate being able to breathe deeply, others see it as a de facto tax, while still another group of automotive unfortunates have cars that won't pass without much expensive work. Whether for purely financial reasons, or a chafing anti-authoritarianism, some drivers elect to circumvent the system.
In California, home of the strictest car emissions regulations in the U.S., cars produced before 1976 do not need to undergo smog testing. California State Senator Dean Florez has proposed legislation that would remove that exemption for cars registered in the San Joaquin Valley Unified Air Pollution Control District.